Chabad.org — English translation + Rashi
Torah Temimah points to Megillah 20b (unit 3; single primary locus per emergency Core plan).
E-Daf.com — Megillah 20b
HebrewBooks / Shas PDF
English: “And he shall atone” — the entire day is valid for the confession of the bull.
All-day window for vidui of the bull — confession over the communal bull may be said any time during the day.
The confession that accompanies the service of the communal bull is valid the entire day. There is no restriction to a particular hour; any time from morning until nightfall satisfies the requirement of vidui for this offering.